Such a separator is used in particular for separating coal particles and for feeding the boiler with particles whose size is smaller than a reference size. The particles whose size exceeds the reference size are recycled to the grinder to be ground again with the coal feedstock.
The particles are conveyed from the grinder to the separator and then to the boiler by a flow air channelled by conveyor ducts. It is known that the hearth of the boiler can be fed via a plurality of ducts. For this reason, the separator commonly includes output compartments, each of which underlies a respective conveyor duct connecting the separator to the boiler.
In existing grinding installations, provision is made to isolate the boiler from the separator by disposing isolating gates on all of the pipes, preferably at the outlets from the separator. In known manner, each gate operates with an air barrier at a pressure that is higher than the pressure upstream and downstream from the gate in the duct in which it is mounted, so that it closes with complete airtightness.
The conveyor ducts connecting the separator to the boiler are closed during certain operations.
However, the use of one isolating gate for each conveyor duct is costly compared with the grinding installation as a whole. The proportionally high cost of isolating the ducts results from the unit cost of a gate, which includes implementing sealing by means of an air barrier, and from the number of gates per grinding installation.